So I recently got my first SES light on a road trip for the weekend. When I got home I had my neighbor help me get the codes off of it.

His machine says. P013801 According to the book for the reader that's a general code for oxygen sensor. I've searched for the code on here and turned up nothing.

I've tried to reset the code a few times now and the light always comes back. At this point I'm leaning towards replacing the oxygen sensor. The car is still running fine.

I have a few questions:

Where is the best place to get the sensor? Summit racing has one for $39 but it looks like you have to take the harness apart and rewire it. Are they all like that aftermarket? What is the O2 sensor to buy?

Am I going to need the special socket for sure or should I give it a try with an open end wrench first? It looks like the radiator has to come out to remove it. We're talking front O2 by the turbo.

Any advise would be appreciated.

 

No word? This is a stock evo BTW, except exhaust, air filter, fuel pump, tune.

Is it worth just trying to take the old O2 sensor out and cleaning it?

 

My service manual lists no P013801 code (2003 Evo). However, it does list a P0138 code. According to the manual the P0138 is set when the rear oxygen sensor is outputting a nonsensical high voltage. This sensor is located at the rear of the catalytic convertor and its reason for being is to test whether the catalytic convertor is working or not.

 

Hmm..? I don't have a cat since my evo is offroad only... =) Alaska is good for that. It was like that when I bought it.

I assume that the rear o2 had to be disabled somehow prior to me buying it since I've owned it for near 3 years and this is the first the code has shown up. That's what made me think it must be the front o2 sensor.

I guess I'll have to investigate the rear o2 further. Thanks.

 

It could be it has been that way for the three years. This code is only set after constant speed driving on the highway. Three years might be a record but I know other people who have removed the rear O2 and have gone awhile, usually a matter of days or weeks, before encountering the code.